The human rights activist Ni Yulan, disabled after being beaten by police, lay on a bed in court and used an oxygen machine to breathe as her trial began today in Beijing.

The former lawyer, 51, is charged with fraud, accused of making false statements to obtain payment, and she and her husband, Dong Jiqin, face charges of "picking quarrels and making trouble". She has pleaded not guilty.

The couple were detained on 7 April while hanging a banner outside the Beijing guesthouse where they were living, after the demolition of their home.

Ni has defended people evicted from their homes by the authorities, including those reportedly moved to make way for the 2008 Olympics.

On Thursday security was tight in the capital around the Xicheng north district court, where Ni became the third high-profile dissident to be tried in a week.

Police sealed off roads to the court and prevented journalists from entering. Diplomats from Britain, Germany, the US and other European countries and the US were allowed to enter the court building, according to the Associated Press.

Ni began opposing forced evictions in 2001, advising residents in her neighbourhood whose homes were listed for demolition as Beijing officials remodelled the city for the Olympics.

In 2002, she was detained while videotaping the demolition of a neighbour's house, and suffered a police beating that broke her ankles and kneecaps.

Since then she has been dependent on a wheelchair and crutches to move around, and suffers multiple health problems, according to Amnesty International.

Her daughter Dong Xuan, who is giving evidence on her behalf, said Ni looked much more frail compared with when she was detained nearly ten months ago, adding: "Seeing my mother lying on that bed, it made my heart ache."

Ni's lawyer, Cheng Hai, had been allowed to see Ni and her husband only two or three times, according to the network Chinese Human Rights Defenders. Appeals for medical parole had received no response.

Dong said she was not optimistic about the outcome of her parents' trial. Referring to the heavy security at the court, she said: "This is definitely not a normal trial procedure, so I feel the risk of conviction is high."

A court spokesman told reporters the case was being heard in accordance with the law. But Sarah Schafer, a China researcher at Amnesty International, said: "We are concerned because this is going to be a huge burden on [Ni], a huge strain on her body and mind." Amnesty had called for Ni's release ahead of the trial.

Ni describes the police beating that partially paralysed her in the documentary Emergency Shelter, by the independent director He Yang. She recalls how police told her she was "minding too many things" that were not her business, before tying her up with rope and systematically pummelling her. "They used their feet and their knees to press against my back, the bone gaps, the acupuncture points, the tendons and bones. They really knew how to beat people up," she said.

She was subsequently convicted of "obstructing official business", and sentenced to one year in prison, with her law licence revoked.

She was arrested again while advising residents campaigning against forced evictions in 2008; her own courtyard home was demolished shortly afterwards.

In the film, Ni says that during her pre-trial interrogation, a police officer [Xiao Wei] from Xicheng district police station "peed in my face" as she knelt on the floor.

Deprived of crutches in prison, and able to move around the building only by crawling on her hands and knees, she was still made to work. "Every day I had to crawl from the upstairs cell down the stairs from the fifth floor … and then across the big prison yard. I had to crawl to the workshop, which was 500 metres away."

After her release, she and her husband were homeless and lived temporarily in a Beijing park. When they rented a small room in a guesthouse they encountered constant harassment, according to the Texas-based Christian support group China Aid.

Two other veteran activists have been handed heavy jail sentences in the past week. A court in Sichuan province sentenced the Tiananmen Square student leader Chen Wei to nine years in prison for publishing online essays critical of the Communist party.

And, on 26 December, Chen Xi got 10 years in prison for publishing online essays and being involved in a human rights forum in Guizhou province. Both men were charged with incitement to subversion.

"The Chinese government seems to be doing its best to put anyone they deem a threat behind bars over the holiday season, when many people around the world are distracted by festivities," said Sam Zarifi, Amnesty International's Asia Pacific director.

On 23 December the government of the Netherlands gave Ni the 2011 Tulip Award for "exceptional courage" in defending human rights. Ni, a Christian, was nominated by China Aid Association and Christian Solidarity Worldwide.